Shahid Umar

Nitrate accumulation in plants, factors affecting the process, and human health implications. A review

Leafy vegetables occupy a very important place in the human diet, but unfortunately constitute a group of foods which contributes maximally to nitrate consumption by living beings. Under excessive application of nitrogen fertilizer, these vegetables can accumulate high levels of nitrate and, upon being consumed by living beings, pose serious health hazards. Therefore, efforts are warranted to minimize the accumulation of nitrate in leafy vegetables and its ingestion by human beings. This review focuses on (i) the contribution of vegetables towards dietary nitrate intake by humans, (ii) the nutritional, environmental and physiological factors affecting nitrate accumulation in plants, (iii) the harmful and beneficial effects of nitrate on human health, and (iv) the strategies that may be followed to minimize the nitrate content in plants and its subsequent consumption by human beings. The risk to human health due to nitrate consumption may be minimized by harvesting vegetables at noon, removal of organs rich in nitrate content and cooking of vegetables in water with a low nitrate content. The European Commission Regulation No. 1822/2005 needs to be followed in order to ensure safe levels of nitrate in plants for human consumption.

Nitrogen availability regulates proline and ethylene production and alleviates salinity stress in mustard (Brassica juncea).

Proline content and ethylene production have been shown to be involved in salt tolerance mechanisms in plants. To assess the role of nitrogen (N) in the protection of photosynthesis under salt stress, the effect of N (0, 5, 10, 20 mM) on proline and ethylene was studied in mustard (Brassica juncea). Sufficient N (10 mM) optimized proline production under non-saline conditions through an increase in proline-metabolizing enzymes, leading to osmotic balance and protection of photosynthesis through optimal ethylene production. Excess N (20 mM), in the absence of salt stress, inhibited photosynthesis and caused higher ethylene evolution but lower proline production compared to sufficient N. In contrast, under salt stress with an increased demand for N, excess N optimized ethylene production, which regulates the proline content resulting in recovered photosynthesis. The effect of excess N on photosynthesis under salt stress was further substantiated by the application of the ethylene biosynthesis inhibitor, 1-aminoethoxy vinylglycine (AVG), which inhibited proline production and photosynthesis. Without salt stress, AVG promoted photosynthesis in plants receiving excess N by inhibiting stress ethylene production. The results suggest that a regulatory interaction exists between ethylene, proline and N for salt tolerance. Nitrogen differentially regulates proline production and ethylene formation to alleviate the adverse effect of salinity on photosynthesis in mustard.

GENOTYPIC DIFFERENCES IN YIELD AND QUALITY OF GROUNDNUT AS AFFECTED BY POTASSIUM NUTRITION UNDER ERRATIC RAINFALL CONDITIONS

ABSTRACT A field experiment was conducted in completely rainfed conditions to determine the effect of different potassium (K) levels on yield and quality of two groundnut genotypes, namely GAUG-1 (bunch type or Virginia upright type) and GAUG-10 (spreading type or Virginia runner type) at Junagadh (Saurashtra region of Gujarat state, India) with highly calcareous vertic ustocherpt soil and erratic rainfall conditions. The two genotypes exhibited different response to varying levels of basally applied K (0, 25, 50, and 75u2005kgu2005K2Ou2005ha−1). GAUG-1 responded the best to 25u2005kgu2005K2Ou2005ha−1, while GAUG-10 to 50u2005kgu2005K2Ou2005ha−1. Application of 25 and 50u2005kgu2005K2Ou2005ha−1 increased the pod yield by 31% and 35% in GAUG-1 and GAUG-10, respectively. At maximum water deficit (soil moisture tension – 16.5 bars), during early growth stage (30 DAS), K application increased the stomatal resistance, proline content and leaf-K content and, thereby, decreased the transpiration rate, resulting in enhanced level of RWC, NRA, and chlorophyll content of leaf in both the genotypes. Thus, potassium application helped in achieving a better crop survival with improved yield and quality of groundnut under water deficit caused by erratic rainfall conditions.

Andrographis paniculata: a critical appraisal of extraction, isolation and quantification of andrographolide and other active constituents

Andrographispaniculata, referred to as ‘Kalmegh’ in ancient texts, is regarded as a nostrum of the modern world. Oral administration of the leaves of this plant is effective in the treatment of upper respiratory tract infections, liver toxicity and a variety of other ailments. The practices of adulteration in the original material of this drug have made it imperative to develop techniques to verify the authenticity of the products of this plant for quality assurance. Andrographolide, a bitter diterpenoid, is the major active principle present in the plant, and therefore its determination and quantification in the plant extracts are important. This article provides a detailed account of various extraction and chromatographic techniques used for the identification, isolation and quantification of the various active principles of A. paniculata. Pharmacological properties and phytochemistry of this plant and the physico-chemical properties of these bio-compounds have also been outlined.

Effect of foliar fertilization of potassium on yield, quality, and nutrient uptake of groundnut

Abstract Groundnut (Arachis hypogae L.) is the most important oilseed crop of India and it is abundantly grown under rainfed conditions in vertisols of Western India. The objective of this work was to study the effect of potassium (K) basal and foliar fertilization on yield, nutrient concentration in tissue and quality parameters of groundnut. Two varieties, GAUG‐1 (bunch type) and GAUG‐10 (spreading type) were grown during Kharif (rainfed) and Rabi (irrigated) seasons at Junagadh, Gujarat. The experiment compared two foliarapplied K fertilizers (KCl and K2SO4) at two different doses (0.5 and 1.0%) with basal KCl application (0 and 50 kg K2O ha−1). Field soil was highly calcareous (pH 8.2, NH4OAc extractable K 188 kg ha−1 with 40% lime reserve) Vertic ustochrept. The results showed a significant response in pod yield with foliar and soil‐applied potassium as compared to the control treatment. Pod yields were significantly higher when basal and foliar applications were combined. The best results were achie...

Factors Responsible for Nitrate Accumulation: A Review

Leafy vegetables occupy a very important place in the human diet, but unfortunately, constitute a group of foods, which contributes maximally to nitrate consumption by living beings. Under excessive application of nitrogen fertilizer, these vegetables can accumulate high levels of nitrate and, on being consumed by living beings, pose serious health hazards. Therefore, efforts are warranted to minimize the accumulation of nitrate in leafy vegetables and its ingestion by human beings. This review focuses on (a) the contribution of vegetables towards dietary nitrate intake by humans, (b) the nutritional, environmental and physiological factors affecting nitrate accumulation in plants, (c) the harmful and beneficial effects of nitrate on human health, and (c) the strategies that may be followed for minimizing the nitrate content in plants and its subsequent consumption by human beings. The risk to human health due to nitrate consumption may be minimized by harvesting vegetables in the noon, removal of organs rich in nitrate content and cooking of vegetables with water having a low nitrate content. The European Commission (EC) Regulation No. 1822/2005 needs to be followed in order to ensure safe levels of nitrate in plants for human consumption.

Influence of Combined Application of Potassium and Sulfur on Yield, Quality, and Storage Behavior of Potato

Abstract In a sand culture study, potato (Solanum tuberosum L.) was grown to maturity in the greenhouse to study the effects of factorial application of four levels, each of potassium (K) (2, 4, 8, and 12 meq L−1) and sulfur (S) (1, 2, 4, and 6 meq L−1), on yield, quality, and storage behavior of tubers. In general, the effect of K was more pronounced than that of S on overall crop performance. Increasing K and S levels in the nutrient medium increased tuber yield as well as dry matter content. The highest tuber yield and percent dry matter content was recorded at 8 meq K L−1, which surpassed the lowest K level by 73% in tuber yield and by 2.5% in percent dry matter content. As compared to the lowest S level, application at 4 and 6 meq S L−1 enhanced average tuber yield and percent dry matter content by 28 and 0.41%, respectively. Similarly, percent starch and protein content of the tuber were also highest at 8 and 12 meq K L−1, surpassing the lowest K level by 8.3–8.4% and 3.2–3.3%, respectively. The effect of S levels was nonsignificant on starch content, while 6 meq S L−1 exceeded the lowest S level by 1.8% in protein content. In contrast, reducing sugars of the tuber decreased gradually with the increase in applied K, revealing the role of K in lowering the tuber reducing sugars content of potato, important for maintaining commercially viable color of potato chips. However, increase in S application did not affect the tuber reducing sugars significantly. Leaf N content was highest at 12 meq L−1, increasing progressively with increasing N levels. Whereas, leaf K and S contents were highest at 8 and 4 meq K L−1, respectively, decreasing significantly thereafter. Increasing S levels increased S content, but decreased tissue K content, significantly. Nitrogen levels increased with 2 meq S L−1, but did not increase thereafter with increasing levels of applied sulfur. 8 meq K × 6 meq S L−1 proved the best Interaction both for tuber yield and dry matter content. Potassium, applied with sulfur, also improved the shelf life of tubers, determined as the percent weight loss of tubers after the storage of four weeks at room temperature, the best interaction with lowest tuber moisture loss being 12 meq K L−1 × 6 meq S L−1.

MODULATION OF NITROGEN-UTILIZATION EFFICIENCY IN WHEAT GENOTYPES DIFFERING IN NITRATE REDUCTASE ACTIVITY

The plants growing in natural field conditions do not express their full genetic potential of nitrogen (N) utilization due to a limiting availability of N at later stages of growth. Their full potential is likely to manifest under non-limiting nitrogen supply wherein the high nitrate reductase (HNR) and the low nitrate reductase (LNR) genotypes should differ significantly in their N-utilization efficiencies. In a sand culture experiment, using IC 321157 (HNR) and C 306 (LNR) genotypes of Triticum aestivum L. under controlled conditions, 15-day-old plants were collected in triplicate and analyzed for nitrate content, N-metabolizing enzymes and N harvest. Kinetic studies were conducted to obtain the Km and Vmax values for enzymes. The values for nitrate content, activities of the nitrate- and the ammonium- assimilating enzymes, biomass and N harvest were higher in the HNR than in the LNR genotype. The higher affinities of enzymes to their substrates in the HNR genotype indicated a greater potential of this genotype for N utilization under non-limiting N supply with a well-coordinated system of N uptake and assimilation. The study suggests that the N-utilization efficiency of plants can be improved by exploiting their full genetic potential under non-limiting N supply, which may be achieved by synchronizing the supply with demand during late stages of plant growth. It also shows that the enzymes responsible for N assimilation act in a coordinated way, thus necessitating the need of a holistic approach for the study of the N-metabolic pathways.

Functional and structural changes associated with cadmium in mustard plant : Effect of applied sulphur

Abstract The effect of cadmium (Cd) and sulphur (S) on dry weight, biochemical parameters and anatomical features of mustard (Brassica campestris L. cv. Pusa Bold) plant was investigated in a pot culture experiment using Cd (25, 50, and 100 mg kg−1 of soil), S (40 mg kg−1 of soil), and the combination of Cd+S (25+40 mg kg−1 of soil, 50+40 mg kg−1 of soil, and 100+40 mg kg−1 of soil). Sulphur treatment was given at sowing and Cd treatment was given when seedlings were fully established. Observations were recorded at the flowering stage. A significant and antagonistic interaction of Cd and S was observed. Compared to the control, leaf dry weight, total chlorophyll content, sugar content, nitrate reductase activity, and protein content decreased significantly with each Cd treatment, whereas the reverse was observed with S treatment. Combined treatments of Cd+S also reduced these parameters, but this reduction was less than the one observed with Cd treatments alone. However, nitrate accumulation in the leaves was 2.35 times higher with treatment of 100 mg Cd+40 mg S kg−1 of soil than in the controls, whereas it was 3.5 times higher with Cd (100 mg kg−1 of soil) alone. The relative proportion of vasculature in the stem, stoma length and width, and stomata length and width were inhibited with Cd treatments, whereas the combined treatments mitigated the adverse effect caused by Cd. Thus, S could alleviate the Cd induced impairment of biochemical and anatomical features of the plant and the enhancement of nitrate accumulation in the leaves.

Symbiotic Nitrogen Fixation by Lentil Improves Biochemical Characteristics and Yield of Intercropped Wheat Under Low Fertilizer Input

To preserve the soils from deterioration caused by the overuse of fertilizers and also because of the continuous price increase of mineral fertilizers, alternative ways must be adopted to reduce their use in agriculture. On the other hand, the increasing world population demands high crop production to meet the food needs in the future. Intercropping grain legumes and cereals can solve the problem because of its high overall productivity and less fertilizer requirements. In this regard, an experiment was conducted to study the effect of three fertilizer application rates (N0K0, N20K50, and N40K50) on wheat/lentil intercropping system. Enhancement in chlorophyll content, nitrate reductase activity, nitrite reductase activity, glutamine synthetase activity, glutamate synthase activity, protein content, and seed yield occurred at lower nitrogen level (N20) in sole and intercropped lentil and at higher nitrogen level (N40) in sole wheat. On the other hand, intercropped wheat exhibited maximum productivity at lower nitrogen rate (N20). Intercropping affected biochemical characteristics and yield of wheat and the system-required low fertilizer input, thus reducing negative environmental impacts of agricultural crop production.